Vulcanizable bromine-containing fluororubber composition containing a peroxy-benzoate

ABSTRACT

A vulcanizable rubber composition which contains an iodine- or bromine-containing rubber and an organic peroxide of the formula. ##STR1## wherein R 1  is a hydrogen atom, a chlorine atom or methyl group, R 2  is a linear or branched alkyl group having 2 to 5 carbon atoms, and n is an integer of 1 to 3, generates only a small amount of methyl iodide or methyl bromide during the vulcanization.

This application is a divisional of application Ser. No. 07/858,505,filed on Mar. 27, 1992, now U.S. Pat. No. 5,296,549, the entire contentsof which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a vulcanizable rubber composition.

2. Description of Related Art

A cured material prepared by vulcanizing an iodine- orbromine-containing rubber is used in various fields. Hitherto, a largeamount of methyl iodide or methyl bromide is generated when the iodine-or bromine-containing rubber is vulcanized with a peroxide. Methyliodide and methyl bromide are poisonous and disadvantageous in view ofenvironmental health.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a vulcanizable rubbercomposition comprising an iodine- or bromine-containing rubber and aperoxide, which composition generates only a small amount of methyliodide and methyl bromide during the vulcanization.

This and other objects are achieved by a vulcanizable rubber compositionwhich comprises an iodine- or bromine-containing rubber and an organicperoxide of the formula: ##STR2## wherein R¹ is a hydrogen atom, achlorine atom or methyl group, R² is a linear or branched alkyl grouphaving 2 to 5 carbon atoms, and n is an integer of 1 to 3.

DETAILED DESCRIPTION OF THE INVENTION

A characteristic of the present invention resides in the use of theorganic peroxide (I) as a curing agent in the composition.

Specific examples of the organic peroxide (I) are t-amyl peroxybenzoate,t-hexyl peroxybenzoate, 1,1,3,3-tetramethylbutyl peroxybenzoate, t-amylperoxy-m-methylbenzoate, t-hexyl peroxy-m-methylbenzoate,1,1,3,3-tetramethylbutyl peroxy-m-methylbenzoate, t-hexylperoxy-p-methylbenzoate, t-hexyl peroxy-o-methylbenzoate, t-hexylperoxy-p-chlorobenzoate, bis(t-hexyl peroxy)phthalate, bis(t-amylperoxy)isophthalate, bis(t-hexyl peroxy)isophthalate, bis(t-hexylperoxy)terephthalate and tris(t-hexyl peroxy)trimellitate. An amount ofthe organic peroxide is generally from 0.1 to 5, preferably from 0.2 to3 parts by weight per 100 parts by weight of the iodine- orbromine-containing rubber.

The iodine- or bromine rubbers are not limited. The iodine- orbromine-containing rubber may be a brominated butyl rubber, and aniodine- or bromine-containing fluororubber. The iodine- orbromine-containing fluororubber is particularly preferable. Specificexamples of the iodine- or bromine-containing fluororubber are describedin U.S. Pat. Nos. 4,243,770, 4,035,565 and 4,214,060, the disclosures ofwhich are incorporated herein by reference.

The composition according to the present invention may contain aniodine- or bromine-free rubber, a cross-linking aid and a reinforcingagent. The iodine- or bromine-free rubber is not limited. Although itmay be a usual rubber, it is preferably a rubber which can be vulcanizedwith an organic peroxide. An amount of the iodine- or bromine-freerubber is usually from 0 to 80, preferably from 0 to 50% by weight basedon the composition. The cross-linking aid is reactive to a peroxy freeradical and a polymer radical. Specific examples of the cross-linkingaid are a triallyl compound (for example, triallyl cyanurate andtriallyl isocyanurate), a diallyl compound (for example, diallylphthalate) and the like. An amount of the cross-linking aid is usuallyfrom 0 to 10, preferably from 1 to 6% by weight based on thecomposition. Specific examples of the reinforcing agent are carbon blackand the like. An amount of the reinforcing agent is usually from 0 to80, preferably from 5 to 50% by weight based on the composition.

The composition according to the present invention can be prepared by agenerally used mixing method using rolls for rubber, a pressurizingkneader and the like. The composition according to the present inventioncan be vulcanized under conditions which are used for vulcanizing ausual rubber. For example, the rubber composition is mixed by rolls, thecomposition is injected in a mold, a press vulcanization is conducted at100° to 200° C. and 20 to 100 kg/cm² G for 5 to 1.80 minutes, and thenan oven vulcanization is optionally conducted in an oven at 150° to 300°C. for 10 to 240 minutes to prepare a vulcanized rubber.

PREFERRED EMBODIMENTS OF THE INVENTION

The present invention will be illustrated by the following Exampleswhich do not limit the present invention.

EXAMPLE 1

An iodine-containing rubber [Dai-el G-902 (vinylidenefluoride/hexafluoropropylene/tetrafluoroethylene terpolymer manufacturedby Daikin Industries, Ltd.)] (100 parts by weight), MT-carbon black(MT-C) (20 parts by weight), triallyl isocyanurate (TAIC) (4 parts byweight) and t-hexyl peroxybenzoate (1.5 parts by weight) as an organicperoxide were homogeneously mixed by rubber rolls to prepare avulcanizable composition.

Vulcanizability of the composition was evaluated by a curastometer at150° C. and 160° C. A lowest viscosity (M_(L)), a highest viscosity(M_(H)), an induction time (T₁₀) and an optimal vulcanization time (T₉₀)were measured. The composition was press vulcanized at 150° C. for 10minutes and then oven vulcanized at 180° C. for four hours to prepare asample of 1 mm thickness.

At ordinary state and after aging at 230° C. for 70 hours, a 100%tensile stress (M₁₀₀), a tensile strength at break (T_(B)), anelongation at break (E_(B)) and a hardness (Hs) were measured.

A compression set (C.S.) was measured for a sample of 13 mm thicknessprepared by vulcanizing in the same conditions as in the above.

An amount of generated methyl iodide was measured when the compositionwas vulcanized at 160° for 10 minutes. The amount of generated methyliodide was measured by charging the vulcanizable composition in a closedvessel, vulcanizing the composition and then determining the amount ofmethyl iodide present in a vacant part of the vessel by means of a gaschromatography.

Results are shown in Table.

EXAMPLE 2

The same procedure as in Example 1 was repeated except that the organicperoxide was used in an amount of 0.8 part by weight. Results are shownin Table.

EXAMPLE 3

The same procedure as in Example 1 was repeated except that the organicperoxide was used in an amount of 0.4 part by weight. Results are shownin Table.

COMPARATIVE EXAMPLE 1

The same procedure as in Example 1 was repeated except that2,5-dimethyl-2,5-di(t-butylperoxy)hexane (Perhexa 2.5 B manufactured byNippon Oil and Fats Co., Ltd.) (1.5 parts by weight) was used as theorganic peroxide and the press vulcanization was conducted at 160° C.for 10 minutes. Results are shown in Table.

                  TABLE                                                           ______________________________________                                                      Com.                                                                          Ex. 1  Ex. 1   Ex. 2   Ex. 3                                    ______________________________________                                        G-902           100      100     100   100                                    MT-C            20       20      20    20                                     TAIC            4        4       4     4                                      Peroxide 1*     1.5      --      --    --                                     Peroxide 2*     --       1.5     0.8   0.4                                    Vulcanizability (160°C.)                                               M.sub.L (kg · f)                                                                     0.12     0.23    0.24  0.18                                   M.sub.H (kg · f)                                                                     3.80     7.20    7.55  4.40                                   T.sub.10 (min.) 0.8      0.3     0.3   0.5                                    T.sub.90 (min.) 2.8      0.7     1.0   2.0                                    Vulcanizability (150° C.)                                              M.sub.L (kg · f)                                                                     --       0.24    0.22  0.21                                   M.sub.H (kg · f)                                                                     --       5.80    4.80  3.75                                   T.sub.10 (min.) --       0.3     0.5   0.7                                    T.sub.90 (min.) --       1.2     2.3   4.3                                    Vulcanizing condition                                                         Press vulcanization                                                           Temperature (°C.)                                                                      160      150     150   150                                    Time (min.)     10       10      10    10                                     Oven vulcanization                                                            Temperature (°C.)                                                                      180      180     180   180                                    Time (hr.)      4        4       4     4                                      Properties at ordinary                                                        state                                                                         M.sub.100 (kg · f/cm.sup.2)                                                          92       100     100   69                                     T.sub.B  (kg · f/cm.sup.2)                                                           208      193     169   187                                    E.sub.B (%)     160      160     160   210                                    Hs (JIS A)      74       74      74    74                                     Compression set (%)                                                                           21       20      25    40                                     (200° C. × 72 hrs.)                                              Amount of generated                                                                           258      49      26    12                                     methyl iodide                                                                 (mg/kg-comp)                                                                  Aging resistance                                                              (230° C. × 70 hrs.)                                              ΔM.sub.100 (%)                                                                          -26      -19     -11   -3                                     ΔT.sub.B (%)                                                                            -14      -10     -21   +11                                    ΔE.sub.B (%)                                                                            +13      +13     +12   ±0                                  ΔHs (point)                                                                             -1       -1      -2    -1                                     ______________________________________                                         Note)                                                                         Peroxide 1: 2,5Dimethyl-2,5-di(t-butylperoxy)hexane                           Peroxide 2: tHexyl peroxybenzoate                                        

What is claimed is:
 1. A vulcanizable rubber composition which comprisesa bromine-containing fluororubber and an organic peroxide of theformula: ##STR3## wherein R¹ is a hydrogen atom, a chlorine atom ormethyl group, R² is a linear or branched alkyl group having 2 to 5carbon atoms, and n is an integer of 1 to 3, wherein an amount of theorganic peroxide is from 0.1 to 5 parts by weight per 100 parts byweight of the fluororubber.
 2. The composition according to claim 1,wherein the organic peroxide is selected from the group consisting oft-amyl peroxybenzoate, t-hexyl peroxybenzoate, 1,1,3,3-tetramethylbutylperoxybenzoate, t-amyl peroxy-m-methylbenzoate, t-hexylperoxy-m-methylbenzoate, 1,1,3,3-tetramethylbutylperoxy-m-methylbenzoate, t-hexyl peroxy-p-methylbenzoate, t-hexylperoxy-o-methylbenzoate, t-hexyl peroxy-p-chlorobenzoate, bis(t-hexylperoxy)phthalate, bis(t-amyl peroxy)isophthalate, bis(t-hexylperoxy)isophthalate, bis(t-hexyl peroxy)terephthalate and tris(t-hexylperoxy)trimellitate.
 3. The composition according to claim 1 whereinsaid rubber is a brominated butyl rubber.